The invention is in the field of the packaging technology and concerns a method and a device for strapping or wrapping objects, particularly substantially parallelepipedic objects.
Substantially parallelepipedic objects such as, for example, stacks of newspapers or magazines, are strapped with tape and/or are wrapped with foil or paper to hold them together and/or to protect them against damage and dirt.
One of the known methods for producing such strapping comprises conveying the object to be strapped to a strapping position. At the strapping position, the strapping material (tape, foil, paper) is positioned to extend curtain-like perpendicular to the conveying direction and across the conveying path. The strapping material is drawn along with the object to be strapped. Thus, the strapping material is placed against the downstream side of the object and can be closed and separated at the upstream side of the object. Accordingly, the object is strapped substantially parallel to the conveying direction and the strapping material again extends across the conveying path ready for the next strapping operation.
The strapped object is conveyed out of the strapping position in the conveying direction, which is substantially the same as the conveying direction to the strapping position. The completed strapping of the object comprises two points in which two ends of the strapping material are connected together, typically by welding, one point on the upstream side of the object and one point on the downstream side of the object.
For strapping methods as described above, the strapping material (tape for strapping or foil or paper for wrapping) is usually supplied from two supply rolls. One supply roll is positioned on each side of the conveying path on which the objects to be strapped are conveyed to the strapping position and away from the strapping position. For each strapping operation the same amount of strapping material is drawn off each supply roll. Controlled deceleration means are usually provided between the conveying path and the supply rolls for controlled drawing of strapping material from the supply rolls and, in particular, for tensioning the strapping material around the objects to be strapped. Furthermore, intermediate storage means is provided in most cases between the deceleration means and the supply rolls. The intermediate storage means stores strapping material drawn from the rolls such that the supply rolls, which usually have a considerable weight, need not be accelerated and decelerated for each strapping operation. Therefore, the intermediate storage means permits a greater drawing-out speed of the strapping material.
When using the known methods and devices for strapping or wrapping as described above it is inevitable that each completed strapping comprises two connection points. It is also inevitable that strapping material needs to be supplied from two sides of the conveying path. This means that, on two sides of the conveying path, supply means and space for the supply means must be provided. This also means that the free ends of the strapping material, supplied from the two sides, must be connected in a special connecting step before a first strapping operation (e.g. after a change of the supply rolls).